Posts Tagged ‘Hexavalent Chromium’

In response to a draft scientific review released in September 2010, the EPA has issued guidance to all public water systems (PWS) recommending enhanced monitoring and sampling programs specifically for hexavalent chromium [also known as chromium-6 or Cr(VI)] in drinking water.

Background
Today there are two common colorimetric techniques using a Diphenylcarbazide (DPC) solution for determining Hexavalent Chromium (Cr+6) in RCRA site water samples. EPA Method 7196, a colormetric method, analyzes the untreated or filtered sample as is. EPA Method 7199, an ion chromatographic method, separates the Cr+6 ion from interferences and is then followed by post column reaction with DPC. Therefore, colored matrices or matrices containing chemical interferences may be better analyzed by ion chromatography as shown in the following example.

A number of relatively new chemical compounds are becoming more significant from a regulatory standpoint. These are commonly called “emerging chemicals” or “emergent chemicals”, which simply refers to the fact that they are coming into view as potential bad actors from a human health and ecological risk standpoint. Some of the chemicals are not particularly new in terms of environmental monitoring (e.g. Hexavalent Chromium, 1,4-Dioxane, etc.), but lower detection limits are required or about to be required. Other compounds are relatively new compared to the routine lists of SOCs and VOCs that have been reported for the past several decades. As discussed in a separate article of this issue of the CAS Connection, Polybrominated Diphenyl Ethers (PBDE) is a class of compounds that have attracted a great deal of attention just within the last year or two. Another subset of compounds that is generally referred to as Personal Care Products (PCP) is also a topic of considerable discussion. Examples of these are antibiotics, estrogens, analgesics, etc. Of the PCPs, some are known to be endocrine disrupters.

Studies are underway in a number of private and government organizations to gain more knowledge regarding the relative propensities for certain compounds to disrupt the endocrine systems of various living organisms, including mammals. CAS is staying abreast of these emerging chemicals and continuously working to bring viable methods on line. In some cases, relatively sophisticated procedures are in place to satisfy new requirements. The table above lists a few of the procedures for analysis of emerging chemicals that CAS is currently performing.